Spray gun



Sept. 1, 1936. R w TRACY 2,052,953

SPRAY GUN Filed Nov. 18, 1931 attorneys Patented Sept. 1, 1936 PATENT OFFICE SPRAY GUN Robert W. Tracy, Toledo, Ohio, assignor to The De Vilbiss Company, Toledo, Ohio, a corporation of Ohio Application November 18, 1931, Serial No. 575,726 4 Claims. (01. ass-140.1)

Thisinvention relates to a spray gun of the type used in spray coating.

The principal object-oi the invention is to simplify and otherwise improve the needle valve assembly, including the mounting for the needle and the means for controlling it. In the present construction, the opening and closing, of the needle valve is controlled by a piston which is reciprocable within a cylinder adapted to be con- 10 nected to a source of compressed air. The range of the piston is adjusted by means of a hollow screw and the piston has a substantial tail rod which is guided within the hollow adjusting screw to insure the proper alignment of the piston with- 15 out depending upon the piston leather or the needle. The needle extends through the tail rod of'the piston andis removable from the gun without removing either the piston or the cylinder. This also facilitates the removal and replacement 20 of the packing for the needle.

The above and other features of the invention will be more fully described in connection with I the accompanying drawing, in which- Figure l is a central longitudinal section of a 25 {gun constructed in accordance with the inven- Figure 2 is a cross-section taken on the line 2-2 of Fig. 1; and

Figure 3 is a longitudinal sectional view of the 30 rear end of the gun, showing a modified construction.

As illustrated in the drawing, the spray gun to which the invention relates comprises a body 5 formed with a passageway 6 for the coating ma- 35 terial, which is delivered through a nipple I secured in the front end of the body. The flow of the material from the nipple I is controlled through the medium of a needle valve 8.

The body 5 is also provided with an air passage- 40 way 9 leading to an'air nozzle l mounted in cooperative relation to the nipple I. In the preferred construction, the air nozzle Ill is provided with a central orifice II which receives the front end of the nipple 1 and with side jet orifices I2, 45 through which air jets are discharged for fiattening the spray. The nozzle per se constitutes no part of the present invention and need not be specifically described. I

For adjusting the how of air through the pas- 50 sageway 9, a plug I3 is mounted transversely of the passageway and is provided with a tapered valve l4, which is splined within the plug and is adjustable transversely of the passageway by means of a thumb screw l5.

' 55 For controlling the operation of the needle valve 8 a piston I6 is reciprocably mounted in a cylinder H, which is secured at one end to the body by an air .tight joint I 9. The piston is provided with a heavy leather 20, which is secured thereto by a follower ring 2| and nut 22. Com- 6 pressed air is supplied to the front end of the cylinder I! through a passageway I9 formed in the body 5.

The rear end of the cylinder I1 is closed by a head 23 into which is screwed a hollow adjusting 10 screw 24, the latter being secured in its adjusted position by means of a lock nut 25.

Normally, when the compressed air is, shut of! from the passageway IS, the piston I6 is maintained in its foremost or inactive position by means ofa spring 26 acting between the ring 2| or some other part of the piston and the cylinder head 23. The piston I6 is formed with an annular shoulder 21, which is adapted to engage the inner end of the adjusting screw 24 to limit the rearward movement of the piston when compressed air is admitted through the passageway I9 to the front end of the cylinder. The piston is also formed with a substantial tail rod 28 which is guided within the hollow adjusting screw 24 and maintains the piston in proper alignment without depending on the piston head or the needle.

The rear end of the needle 8, as shown in Fig. 1, carries adjustable nuts 29, which are engageable 30 by the rear end of'the tail rod 28 to open the needle valve. As soon as the compressed air is shut off from the passageway Hi, the piston is advanced by the spring 26 and the needle valve is closed by a spring 30, which is seated within the head of the hollow adjusting screw 24 and acts against the nuts 29. I

The central part of the body 5 is provided with a transverse opening 3| through which packing 32 and 33- may be inserted. This packing is held in place by screw plugs 34 and 35;

It will be noted that there is normally a space, between the nuts 29 and the tail rod 28 whenthe pressure is shut off. This allows a positive seating of the needle valve and also causes a quick opening of the same by the action of the piston when the pressure is turned on.

In order to remove the needle from the gun,

- it is only necessary to remove the adjusting screw 24, whereupon the needle may be withdrawn through the rear end of the tail rod 28. With the needle removed it is a simple matter to renew the packing 32 and 33.

In the modification shown in Fig. 3, a head 38 is suitably secured to the rearend of the needle 8 and is covered by a cap 31 which is connected to the rear end of the tail rod 28. In this construction, the parts are so proportioned that the head is revolvable in the cap without end play.

The extent to which the needle valve is opened is determined by the adjustment of the screw 24. The inner end of this screw has a comparatively large bearing surface, which engages directly against the shoulder 21, so that it cannot be damaged by the concussion resulting from the high air pressure.

It is to be understood that the construction shown and described is merely for the purpose of illustration and that the invention includes all such modifications as may fall within the scope of the appended claims.

What I claim is:

a 1. A spray gun comprising a body with a passageway therethrough, a needle valve cooperating with the discharge end of said passageway, a cylinder, a piston reciprocable in said cylinder and operable by fluid pressure to open said needle valve, a hollow adjusting screw with its inner end constituting a stop for the piston when the latter is acted upon by fluid pressure, a hollow tail rod on said piston and through which the rear end of the needle valve projects, and an abutment on saidprojecting end engageable by said tail rod to open the needle valve when the piston is acted on by fluid pressure, said tail rod and'the abutment on theneedle valve being guided within said adjusting screw to maintain their alignment.

2. A spray gun comprising a body with a passageway therethrough and having also an opening in the side thereof, a needle valve cooperating with the discharge end of said passageway and extending across said opening. a cylinder secured to said body, a piston reciprocable in said cylinder and operable by fluid pressure to open said needle valve, a hollow tail rod on said piston and through which the rear end of the needle valve projects,

a hollow adjusting screw limiting the range of the piston and in which the said tail rod and needle valve are guided, saidneedle valve being removable from the gun whenever said adjusting screw is removed, and packing glands for said needle valvev at each side of said opening, said glands bein'g removable from said opening whenever the needle valve is removed.

3. A spray gun comprising a body with a material passageway closed needle valve cooperating with the discharge therethrough, a normally end of said material passageway, a cylinder separate from said passageway, a piston having' an elongated tail r0d reciprocable in said cylinder and operable by fluid pressure to open the needle valve, means yieldingly opposing a fluid pressure actuated movement of the piston, and a hollow member threadedly engaged with the rear of the cylinder to guide said piston by engagement with said tail rod and maintain its alignment, said member constituting also an adjustable abutment to limit the movement of the piston in opening the needle valve.

4. A spray gun comprising a body having a 3 hollow guide means for said tail piece adjustably carried by the rear of said cylinder whereby to guide andlimit the extent of movement of said piston.

ROBERT w. TRACY. 

